UPSC NDA I 2015 General Ability Solved Paper

In astronomy, axial tilt (also called obliquity) is the angle between an object’s rotational axis and the perpendicular to its Orbital plane, both oriented by the right hand rule. At an obliquity of 0°, these lines point in the same direction i.e. the rotational axis is perpendicular to the orbital plane. Axial tilt differs from inclination. Over the course of an orbit, the angle of the axial tilt does not change, and the orientation of the axis remains the same relative to the background stars. This causes one pole to be directed toward the Sun on one side of the orbit, and the other pole on the other side, the cause of the seasons on the Earth.